It's a real number. The ROI is being calculated based on the price of token when he bought it with the current price. It's taken from his wallet address, and you can easily find his solana address.
So many meme traders were always putting his address as their watchlist to know which meme tokens to buy.
Yep, but that's a good case to get the fishes flowing to the shark

Before venturing into memes - there are lots of things to check.
And as it was said - it will probably not be worth it.